The present invention relates to a self-moistening tracheostomy device.
As is well known, a tracheostomy is an operation designed to implant a temporary or permanent by-pass of the upper airways, i.e. of the nose, mouth, larynx and pharynx, and is carried out to ease the patient""s breathing by reducing inspiration and expiration resistance.
Perviousness of the stoma is maintained by means of a cannula inserted into the stoma itself and into the trachea. However, by-passing the upper airways also results in excluding the natural function of these organs, i.e. heating and moistening the air breathed in from the environment before it reaches the lungs. On the other hand, lack of warming and humidification of the air that is breathed in causes in the patients an increase in and a thickening of tracheal secretions with consequent reduction in respiratory efficiency.
To avoid these problems there have for some time been so-called passive humidifiers available that take over the function of the natural organs and the upper airways. Such devices are also known in technical slang as  less than  less than artificial noses greater than  greater than  and are designed to be connected to the external attachment of the tracheostomy cannula.
Such known devices consist of a small box-like plastic shell within which is located a hygroscopic material insert, a kind of filter, that absorbs and conserves the moisture and warmth in the exhaled air to then return it to the inhaled air.
Such inserts can be made using essentially two kinds of materials: open cell polyurethane foams or cellulose.
The open cell polyurethane foam type of insert has the advantage of offering low mechanical resistance to the air, thus improving the inhalation and exhalation operations, but is detrimental to the filter capacity to hold and conserve sufficient warmth and moisture.
The cellulose type of insert, on the other hand, holds heat and moisture satisfactorily but with the disadvantage of offering greater resistance to air permeability.
Another feature distinguishing the type of inserts described above is the fact that the inserts obtained with polyurethane foam can be made into any shape that may be necessary as they are permeable in every direction, whereas the cellulose inserts consist of simple helical folds, e.g. in cylindrical form, that for air to pass through must be necessarily housed in a case or box-like shell in such a way that the inhaled and exhaled air flows go through axially and not at right angles, as permeability is inhibited in the latter direction.
The shape of the body case or shell is of great importance in the making of the said artificial noses as these have also to have at least one attachment for an oxygen supply, in case of need, and a valve through which it is possible to intervene, without removing the tracheostomy device, to aspirate any excess secretions.
As a matter of fact, in the tracheostomy devices with a polyurethane foam insert, for example, it is possible to position the oxygen inlet in any area of the case or box-like shell so that the oxygen can pass through the insert from which ever direction it comes, before descending into the lungs, thus taking on moisture and above all heat, as said, in quite limited quantities.
In the case of cellulose inserts, the position of the oxygen inlet is, on the other hand, necessarily located tangentially and externally to the box-like shell since otherwise, i.e. if it were directed towards the inside of the box-like shell, it would be obstructed by the outer surface of the cellulose cylinder that would therefore impede the supply of oxygen.
The two valves similarly pose problems of location as they must be placed in the body of the box-like shell coaxially to the tracheostomy attachment cannula so that any aspiration can be carried out in line and without difficulty.
The main object of the present invention is that of removing the drawbacks indicated above by providing a self-moistening device for tracheotomies that permits the use of cellulose inserts and therefore a high performance system, with no structural limitations to oxygen inlet and access valve location.
This and other objects that will better appear below are achieved by a self-moistening tracheostomy device according to the present invention that includes a box-like shell and having an entry attachment mouth on one side thereof for the end of a tracheostomy cannula and an inlet opening for oxygen administration, and an exchanger element located inside said box-like shell, characterised in that said exchanger element comprises a plurality of cellulose-type laminar elements.